Hithertofore, in instances in which positive-working presensitized lithographic printing plates and negative-working presensitized lithographic printing plates are processed using a developing solution capable of developing a negative-working presensitized lithographic printing plate and a positive-working presensitized lithographic printing plate in common, there is a processing method in which a fresh developing solution is fed to the surfaces of the plates to be processed and the developing solution having been used is discarded (i.e, a fresh-solution processing method). In another processing method in which a replenishing solution is added to a developing solution so that the developing solution can be repeatedly used (i.e., a circulation method), positive-working presensitized lithographic printing plates and negative-working presensitized lithographic printing plates may cause exhaustion of the developing solution in a degree different from each other, and hence there has been the problem that it is difficult to control the replenishing and is difficult to carry out stable processing in practical use. The fresh-solution processing method has the disadvantage that it consumes the developing solution in a larger quantity than the circulation method.